Do i have frogs or toads? HELP?

Hi a frog/toad layed frogspawn in my pond about a month ago i didn't see it though. But instead of the tadpoles hatching with tails they came out looking like little black lines (they all hatched and about 3 died) and they just lay on the bottom of the pond wiggling from time to time. They have now grown and look like normal tadpoles. I have taken four tadpoles and transfered them into a small tank to have a look at them, they are starting too grow legs and are jet black in colour, I just wonderd as usually I get frogs in my pond and as this time they were differant i was just curiouse. So if anyone can give me some info and tell me what happened thanks! BTW no links please i want written info on the answers :)